Transformation of ellipsoidal heights determined by satellite techniques into local leveling heights requires geoid heights at points of interest. However, the geoid heights at each point are not available. In order to determine them, the local geoid in the transformation area must be modeled or computed by an appropriate method, one way of doing it, is to use control points both of whose ellipsoidal and local leveling heights are available. In this study, performance of geoid by ANN compared to Kriging method in modeling local geoid was presented. Moreover, the transformation ability of the methods was investigated through a geodetic test network in Bursa Metropolitan Area of Turkey. The results suggest that the model by ANN exhibit better results than the one by Kriging Method. Keywords: Geoid; Local Geoid Modeling; ANN; Kriging; Transformations.
RESUMOA transformação das altitudes elipsoidais determinadas por técnicas satelitais em locais de altitudes niveladas requer o conhecimento da altitude geoidal no ponto de interesse. Entretanto, as altitudes geoidais de cada ponto nem sempre estão disponíveis. A fim de determiná-las, um geóide local de transformação deve ser determinado ou calculado através de métodos apropriados. Uma maneira de fazer isto, é usar pontos de controle de ambos cujas altitudes elipsoidais e niveladas estejam disponíveis. Neste estudo, apresenta-se os resultados da comparação entre o geóide obtido por ANN e o método da Krigagem na modelagem do geóide local. Akcin,H. ; Celik, C. T. Bol. Ciênc. Geod., sec. Artigos, Curitiba, v. 19, n o 1, p.84-97, jan-mar, 2013. 8 5 Além disso, a habilidade da transformação dos métodos foi investigada através de uma rede geodésica teste na área metropolitana de Bursa na Turquia. Os resultados sugerem que o modelo por ANN exibe melhores resultados que o método da Krigagem. Palavras-chave: Geóide; Modelamento do geóide local; ANN; Krigagem; Transformações.
In this study, for Istanbul, there are two Cors Networks (Cors-TR, Iski Cors) providing Virtual Reference Station (VRS), and Flachen Korrektur Parameter (FKP), corrections to rover receiver for determining 3-D positions in real time by Global Positioning System (GPS). To determine which method (or technique) provides accurate method for position fixing, a test network consisting of 49 stations was set up in Yildiz Technical University Davudpasa Campus. The coordinates of the stations in the test network were determined by conventional geodetic, classical RTK, VRS and FKP methods serviced by both Cors-TR and Iski Cors. The results were compared to the coordinates by the conventional method by using total station. The results showed a complex structure as the accuracy differs from one component to another such as in horizontal coordinates, Y components by CorsTR_VRS and Cors_TR_ FKP showed 'best' results while the same technique provided X components consistent accuracy with the Y component but less accurate than by real time kinematic (RTK). In vertical components, of all the techniques used for the h components, CorsTR_VRS showed 'best' accuracy with three outliers.
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